1. Field of the Invention
The invention relates to die transfer structures and methods, and refers more specifically to a structure for and method of transferring a die from a die transfer truck to a bolster plate on a press or the like, providing a bolster plate in position on a press with T-slots without machining the bolster plate, centering a die on a bolster plate, and clamping a die to a bolster plate.
2. Description of the Prior Art
In the past, dies have often been placed on a press bolster plate and moved around on the bolster plate manually to align the dies in a desired position. Dies have then been clamped to the bolster plate in a fixed position for use. The dies have often been centered on the bolster plate in these fixed positions.
Prior bolster plates have sometimes been flat on top. However, many of them have T-slots machined in the top surface of the bolster plate to facilitate clamping of dies to the bolster plate. Wherein a bolster plate of the past has been flat on top and it has been desired to put T-slots in the bolster plate, it has usually been necessary to remove the bolster plate from the press on which it is installed, which often requires disassembly of the press. Alternatively, recently it has been possible to machine T-slots in a bolster plate with portable equipment placed on the bolster plate with the bolster plate in the press. Prior to the present invention, however, it has not been known to manufacture structures and secure them to a bolster plate to provide T-slots on the top of the bolster plate.
Further, movement of dies on bolster plates and on die transfer trucks or carts especially designed for movement of dies from storage racks and the like has seldom been facilitated by adequate means for reducing friction between the dies and the bolster plates or table tops of the trucks. Consequently, moving dies, especially the larger ones, onto and off of bolster plates and aligning or centering the dies on the bolster plates has, in the past, usually been a laborious and time consuming job.
Wherein means for reducing friction between a die and a bolster plate or truck table top to facilitate die transfer has been provided in the past, the structure and method provided has usually not facilitated universal movement of the die in the plane of the top of the truck table or bolster plate, and has not provided means for assuring the die transfer truck table is at the same level as the bolster plate during transfer of the die. Such prior systems have also often facilitated transfer of the die only in a straight line.
Accordingly, the die transfer systems of the past have been useful primarily in conjunction with transferring dies on or off of presses where space is unlimited and the desired direction of movement of the die onto the bolster plate is compatible with the direction permitted by the prior die transfer systems. Such systems are, for example, that provided by elongated rollers placed in the truck table and the bolster plate which facilitate movement of the die along a line onto or off of the bolster plate.
In addition, the die transfer systems of the past have generally been unable to accomodate dies with risers attached to the bottom thereof due to the spaces between the bearings of the die transfer systems and the spaces between the risers. Wherein risers have been attached to dies in the past, it usually has been necessary to provide a plate on the bottom of the risers to accomodate prior die transfer systems.
Also, alignment of dies on bolster plates and centering of the dies on the bolster plates has in the past generally been accomplished by manually pushing the dies around on the bolster plate and measuring the position of the dies with respect to a refererence point or lines on the bolster plate or press. The distances from the reference points or lines are different for each press a die is centered on. Such die positioning method is energy and time consuming, tires skilled workmen, and requires down time of the press on which the die is being positioned, which is not economical.
The linear die transfer systems alluded to above only partially eliminate the problems of die alignment in that they only facilitate movement of the die in one direction on a bolster plate or truck table. Further, such linear systems do not provide a centered or exactly aligned die on a bolster plate.
In the past, clamping of dies in position on a bolster plate has been accomplished in a plurality of ways, such as with clamps having a toe on the die and a heel on a block with a bolt in between the two secured in holes or T-slots in the bolster plate or the like. Such clamping is generally not done scientifically in that the holding power of the clamps is varied by the positions of the clamp heel, block and bolt. The clamping force is usually not exactly calculated.
Wherein clamping structures have been provided secured to the die or engaged with the die and secured to the bolster plate immediately adjacent the die, they have been of a nature as to require excessive time in undoing bolts, removing washers and the like during clamping and unclamping of the dies. Automatic clamps are available, however, they are complicated and expensive.